The friendly-traceback project (in early alpha) is working on making traceback messages more helpful and translatable - https://aroberge.github.io/friendly-traceback-docs/docs/html/
On Tue, 14 Jan 2020 at 12:43, Guido van Rossum <gu...@python.org> wrote: > On the subject of replacing the current parser, I am actively working on > that. See GitHub.com/gvanrossum/pegen. > > On Tue, Jan 14, 2020 at 10:32 Andrew Barnert via Python-ideas < > python-ideas@python.org> wrote: > >> On Jan 14, 2020, at 05:22, Σταύρος Ντέντος <stde...@gmail.com> wrote: >> > >> > Hello there, >> > >> > If I have simply missed a double colon starting a for loop >> > >> > File "./bbq.py", line 160 >> > for config_file in config_files >> > ^ >> > SyntaxError: invalid syntax >> > >> > the message is not as straightforward. >> >> I think almost everyone would prefer it if the compiler could say >> “SyntaxError: missing colon at end of a compound statement header” or >> something more useful. >> >> And that probably goes even more for this case: >> >> spam = eggs(cheese, (foo, bar) >> cheese = spam*2 >> >> The problem is to come up with a rule that could be applied to detect >> these cases given the information the simple LR(1) parser has available at >> the time of failure. I suspect there’s no way to do that without radically >> changing the parser architecture, keeping track of a lot more state, or >> partially re-parsing things in the error handler. (If it were easy, Guido >> would have done it back in 1.x.) >> >> But maybe there’s a way to heuristically detect that these problems are >> _likely_ causes of the error (without having to be as ridiculously >> complicated as what Clang does with C++ code)? If you could find a way to >> make the error say “SyntaxError: invalid syntax (possibly missing colon at >> end of compound statement header)” in most simple “forgot the colon” cases >> and very few other cases, without massively disrupting everything, I think >> people would be happy with that. >> >> You might even be able to take advantage of re-parsing without having to >> solve all the problems that go with that. For example, technically, you >> can’t even access the last logical line to reparse; practically, you can >> get it in the same cases the traceback can print it, and those are probably >> the only cases you need to heuristically improve the error handling. You >> could even maybe do a quick & dirty proof of concept in Python in an import >> hook, if you don’t want to dive into the middle of the C compiler code. >> >> As an alternative, there are lots of projects to use more powerful parser >> algorithms on Python. There’s not much call to replace CPython’s parser, >> because there aren’t any benefits to offset the costs. (At least assuming >> that the language is going to stay LR(1), to make it easy to parse in your >> head.) But if you could improve most of the most annoying error handling >> cases, that might be a different story. And these might also be easier to >> play with. (Some have pure Python implementations, and even the ones in C >> aren’t embedded in the middle of the compiler code.) IIRC, early Java did >> something clever with a GLR parser that has LR(1) performance on all valid >> code and strictly bounded complexity on error recovery (so it may get as >> bad as worst-case cubic, but cubic on N<=5 so who cares) so they could >> usually produce error messages as good as most C compilers without the >> horrible mess of parsing that most C compilers need. >> >> _______________________________________________ >> Python-ideas mailing list -- python-ideas@python.org >> To unsubscribe send an email to python-ideas-le...@python.org >> https://mail.python.org/mailman3/lists/python-ideas.python.org/ >> Message archived at >> https://mail.python.org/archives/list/python-ideas@python.org/message/ILJNAN4E5VROSODWO2UWJDHP5DCVM56G/ >> Code of Conduct: http://python.org/psf/codeofconduct/ >> > -- > --Guido (mobile) > _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/OX7USOGCS4ADMSGCRMTTL6JI3SPLNACD/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- Naomi Ceder @NaomiCeder • https://www.naomiceder.tech https://www.manning.com/books/the-quick-python-book-third-edition
_______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/D4JATKCFTU3466OYS35J4ZRTLZL77VOU/ Code of Conduct: http://python.org/psf/codeofconduct/
